Munther K. Homoud

Arrhythmogenic right ventricular dysplasia: clinical results with implantable cardioverter defibrillators.

Arrhythmogenic right ventricular dysplasia is a clinical entitycharacterized by fatty infiltration of the right ventricle and left bundlemorphology ventricular tachycardia occurring in young patients. The mostcommon cause of death is tachyarrhythmic. Pharmacological andnonpharmacological therapies, including implantable cardioverterdefibrillators, have been used to treat the arrhythmias. However, rightventricular endocardial leads in this population may be associated with anincreased risk of perforation and suboptimal sensing and defibrillationefficacy due to the diseased right ventricle. We report on 12 patients witharrhythmogenic right ventricular dysplasia who were treated with implantablecardioverter defibrillators. The mean age was 31± 9 years (range15-48). Patients presented with presyncope (5), syncope (4), or cardiacarrest (3). All patients had electrocardiographic abnormalitiescharacteristic of the condition.Follow-up averaged 22 ± 13months (range 1-45). There was one sudden death at 1 month of follow-up. Ofthe 12 patients, 8 have had appropriate therapy delivered by the implantabledefibrillator. Six patients are currently on sotalol to reduce the frequencyof implantable defibrillator discharges. In conclusion, implantablecardioverter defibrillators with nonthoracotomy leads are feasible and safein patients with arrhythmogenic right ventricular dysplasia. The frequencyof appropriate therapy is high, supporting the use of implantablecardioverter defibrillators in this population.During programmedelectrical stimulation nine patients had sustained ventricular tachycardia,while three patients had no inducible arrhythmia. Transvenous leads wereplaced in nine patients. In these patients pacing thresholds weresignificantly higher, R-wave amplitudes were significantly lower, anddefibrillation thresholds were not significantly different than in a cohortof patients without right ventricular dysplasia. There were no acute orchronic complications of right ventricular lead placement.

Comparison of frequency of complications of implantable cardioverter-defibrillators in children versus adults

Compared with adults patients (n = 309) receiving implantable cardioverter-defibrillators at the same institution, pediatric patients (n = 11) exhibited a trend toward lower defibrillation thresholds. At follow-up of 29 +/- 17 months, the incidence of recurrent arrhythmias was similar, but lead revisions and device infections were more common in the pediatric patients.

Cardiovascular Toxicities of Performance-Enhancing Substances in Sports

Athletes commonly use drugs and dietary supplements to improve athletic performance or to assist with weight loss. Some of these substances are obtainable by prescription or by illegal means; others are marketed as supplements, vitamins, or minerals. Nutritional supplements are protected from Food and Drug Administration regulation by the 1994 US Dietary Supplement Health and Education Act, and manufacturers are not required to demonstrate proof of efficacy or safety. Furthermore, the Food and Drug Administration lacks a regulatory body to evaluate such products for purity. Existing scientific data, which consist of case reports and clinical observations, describe serious cardiovascular adverse effects from use of performance-enhancing substances, including sudden death. Although mounting evidence led to the recent ban of ephedra (ma huang), other performance-enhancing substances continue to be used frequently at all levels, from elementary school children to professional athletes. Thus, although the potential for cardiovascular injury is great, few appropriately designed studies have been conducted to assess the benefits and risks of using performance-enhancing substances. We performed an exhaustive OVID MEDLINE search to Identify all existing scientific data, review articles, case reports, and clinical observations that address this subject. In this review, we examine the current evidence regarding cardiovascular risk for persons using anabolic-androgenic steroids including 2 synthetic substances, tetrahydrogestrinone and androstenedione (andro), stimulants such as ephedra, and nonsteroidal agents such as recombinant human erythropoietin, human growth hormone, creatine, and beta-hydroxy-beta-methylbutyrate.

Analysis of intracardiac electrograms showing monomorphic ventricular tachycardia in patients with implantable cardioverter-defibrillators

Ventricular tachycardia (VT) initiation and its relation to various clinical factors was studied by reviewing intracardiac electrograms from patients with implantable cardioverter-defibrillators. Events were divided into (1) sudden onset without preceding ventricular premature complexes (VPCs), (2) extrasystolic onset with VPCs, or (3) paced, depending on the type and morphology of the last 5 beats before initiation of VT. Prematurity index, sinus rate, cycle length, and presence of short-long-short sequence for each episode was noted. A total of 268 episodes of VT among 52 patients were analyzed. Extrasystolic initiation was the most frequent pattern (177; 66%) followed by sudden onset (75; 28%) and paced (16; 6%). Among extrasystolic onset, 99 episodes (56%) were due to multiple VPCs and 149 episodes (84%) had different VPC morphology than the subsequent VT. Among pacing-induced VT, 13 of 16 episodes were due to inappropriate pacing due to undersensing of prior R waves. Sudden-onset episodes were slower (mean cycle length 383+/-97 ms) than extrasystolic (mean cycle length 336+/-88 ms, p = 0.002) and paced (mean cycle length 313+/-85 ms, p = 0.01) onset. Patients in the sudden-onset group had better left ventricular ejection fraction (33+/-15%) than the extrasystolic (29+/-11%, p<0.001) and paced (28+/-14%, p<0.01) groups. Extrasystolic onset with multiple, late coupled VPCs was the most common pattern of VT initiation and was associated with lower ejection fraction. Sudden-onset initiation was more common with better preserved systolic function.

Long-term outcome of patients with syncope associated with coronary artery disease and a nondiagnostic electrophysiologic evaluation

Syncope in the patient with structural heart disease and a nondiagnostic noninvasive workup is a generally accepted indication for an invasive electrophysiologic study. However, if the electrophysiologic evaluation is not highly sensitive, arrhythmic causes of syncope may not be discovered. In these patients, recurrent syncope and even sudden death may be observed at follow-up. Thus, we evaluated long-term follow-up in 68 consecutive patients who presented with syncope, coronary artery disease, and who had a negative invasive electrophysiologic evaluation. At a mean follow-up of 30 +/- 18 months (range 1 to 65), there have been 2 sudden deaths and 1 episode each of ventricular fibrillation and ventricular tachycardia in patients treated with an implantable cardioverter-defibrillator. All 4 arrhythmias occurred in patients with left ventricular fractions < or = 25%. Seventeen patients had recurrent presyncope or syncope. Bradycardia causing syncope was found in 8 of these patients. A bundle branch block at the initial evaluation predicted for the occurrence of bradycardia at follow-up. We conclude that in patients with coronary artery disease and syncope, noninducibility at electrophysiologic study predicts a lower risk of sudden death and ventricular arrhythmias. However, in patients with a reduced ejection fraction, the risk of sudden death and ventricular arrhythmias remains up to 10%/year and these patients may warrant treatment with implantable cardioverter-defibrillators. Recurrent syncope is common, and frequently a bradyarrhythmia is found to be the cause. Treatment of selected patients (especially those with bundle branch blocks) with permanent pacemakers may be justified.

Cryoablation of the pulmonary veins using a novel balloon catheter.

Introduction. Pulmonary vein (PV) isolation has emerged as a promising technique for the treatment of patients with drug-refractory atrial fibrillation, however, the achievement of transmural lesions has remained a challenge. We evaluated the ability of a novel balloon-based cryogenic catheter system in achieving transmural lesions for PV isolation.Methods. Six pulmonary vein ostia from three excised ovine hearts and lungs were used in this study. The balloon catheter was deployed and positioned at the ostia of the PVs and a full 8-minute ablation was then performed, while the heart was bathed in a circulating bath of normal saline at 37∘. Thermocouples positioned on the endocardial (balloon surface—tissue interface) and epicardial surfaces of the ostia were used to determine whether transmural freezing was achieved.Results. The mean temperatures measured on the endocardial and epicardial tissue in six PV ablations were −38.8∘ ± 6.9∘C and −10.0∘ ± 7.5∘C, respectively. The average pulmonary vein thickness was 3.3 ± 1.4 mm.Conclusions. A novel cryoablation balloon catheter is capable of achieving transmural freezing of the pulmonary vein. The catheter has promise for future clinical therapy of atrial fibrillation.

Microwave radiometric thermometry and its potential applicability to ablative therapy.

Introduction: Current techniques for estimating catheter tip temperature in ablative therapy for cardiac arrhythmias rely on thermocouples or thermistors attached to or embedded in the tip electrode. These methods may reflect the electrode temperature rather than the tissue temperature during electrode cooling so that the highest temperature away from the ablation site may go undetected. A microwave radiometer is capable of detecting microwave radiation as a result of molecular motion. In this study, we evaluated microwave radiometric thermometry as a new technique to monitor temperature away from the electrode tip during ablative therapy utilizing a saline model.Methods and Results: A microwave radiometer antenna and fluoroptic thermometer were inserted in a test tube with circulating room temperature saline kept constant at 23.5°C while the surrounding saline bath was heated from 37°C to 70°C. For every degree rise in the warm saline bath placed either 5mm or 8mm from the radiometer antenna, the radiometer temperature changed 0.26°C and 0.14°C respectively while the fluoroptic temperature probe remained constant at 23.5°C. The radiometer temperature was highly correlated with the warm saline bath temperature (R2=0.997 for warm saline 5mm from the antenna, R2=0.991 for warm saline 8mm from the antenna).Conclusions: Microwave radiometry can estimate distant temperatures by detecting microwave electromagnetic radiation. The sensitivity of the microwave radiometer is also distance-dependent. The microwave radiometer thus serves as a promising instrument for monitoring temperatures at depth away from the catheter-electrode tip in ablative therapy for cardiac arrhythmias.

Syncope in the Patient with Nonischemic Dilated Cardiomyopathy

Over the past decade, syncope has become increasingly recognized as an indicator of poor prognosis in patients with nonischemic dilated cardiomyopathy (NIDCM). In several clinical series, patients with depressed ejection fraction in the absence of significant obstructive coronary artery disease who experience syncope have been shown to be at high risk for sudden death with a corresponding increased rate of ventricular arrhythmias and appropriate implantable cardioverter defibrillator (ICD) therapy. Furthermore, several studies have cast doubt on the prognostic value of electrophysiological studies in these patients. This review presents the body of evidence to date surrounding the clinical implications and management of syncope in this patient population.

Cardiac arrhythmias in the athlete.

Cardiac arrhythmias in the athlete are a frequent cause for concern. Some arrhythmias may be benign and asymptomatic, but others may be life threatening and a sign that serious cardiovascular disease is present. Physicians often are consulted with regard to arrhythmias, or symptoms consistent with arrhythmias, in athletes. Sinus bradyarrhythmias are common and even expected in athletes. These bradyarrhythmias are rarely a cause for concern. Heart block is unusual and merits a thorough workup. Atrial fibrillation may be more common in the athlete. Supraventricular tachycardias other than atrial fibrillation generally warrant consideration of radiofrequency ablation for cure of the tachyarrhythmia. Ventricular arrhythmias in the athlete generally occur in the setting of structural heart disease that is genetically determined (hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, anomalous coronary arteries) or acquired (coronary artery disease, myocarditis, idiopathic dilated cardiomyopathies). In these conditions, the arrhythmia generally is life threatening. Ventricular arrhythmias that occur in the athlete without structural heart disease are not thought to be life threatening. Athletes with structural heart disease and syncope and those with exertional syncope merit a complete evaluation.

Use of antiarrhythmics and implantable cardioverter-defibrillators in congestive heart failure.

As much as half of the mortality in patients with congestive heart failure (CHF) resulting from left ventricular systolic dysfunction is attributable to sudden cardiac death. Thus, the identification of risk and prevention of sudden death are important components of treating this population of patients. Antiarrhythmic drugs have been shown to be either neutral or harmful when studied in patients with prior myocardial infarction and impaired left ventricular function. Amiodarone, when studied in patients with CHF, may be of benefit. This benefit may be more pronounced in patients with nonischemic cardiomyopathy. Implantable cardioverter defibrillators (ICDs) are of clear benefit when used in the primary and secondary prevention of sudden death in selected populations. Studies soon to be completed should clarify the role of the cardioverter-defibrillator in patients with CHF. Antiarrhythmic medications are often used in conjunction with ICDs for a variety of reasons. However, these drugs have the potential to adversely affect defibrillator function, and knowledge of these effects is important when using this strategy.